Hi all Can you please assist on how to recover deleted e-mails that was deleted 4months back, we are on Exchange 2010 and the retention policy for deleted mails on the exchange server is 14 days. the other thing the backup was having some issues on that particular time so the backup can`t rescue me.

I'm sorry to say this, but you can't.  The data in the databases has been overwritten by now, and since you have no valid backup, you can't bring these emails back in any other manner.

Will is 100% correct and just to clarify you have no backups at all pre/post the activity your trying to recover?

Agreed with above suggestions.

The deleted items can be recovered only if you have valid backup is available.

As you said, you do have some issues into your backup, some third party tools (like, http://www.restoreexchange.net/) can help you to extract the items even if backup is corrupt. Ultimately, you should have a valid backup available.

You can configure new retention policy following this informative resource : https://technet.microsoft.com/en-us/library/ff715341%28v=exchg.141%29.aspx